Sweat, or perspiration, is often produced during physical activity and, to keep the body functioning optimally, lost fluids have to be replenished. For sports people it is particularly important to ensure adequate hydration. However, it is known that drinking too much fluid can be detrimental, possibly even more so than drinking too little fluids.
As individuals sweat at different rates, and sweating also depends on climatic conditions and the individual's level of activity, it can be quite difficult to accurately estimate the amount of fluid required at any given time to maintain proper hydration for individuals engaged in physical activities. Such activities include sport, work and military activities. Proper hydration is particularly important where the activities take place in deserts and other hot or high humidity environments.
It is also critical with some diseases which can induce high levels of dehydration, such as malaria, that hydration be carefully monitored and controlled.
Methods of measuring sweat production are available, but are typically quite complex. These methods mostly rely on measurements of conductivity on the skin and hence require electronic equipment to function. As such, these devices are fairly complex and may be difficult to use during normal sporting events or by many individuals simultaneously.
A method of measuring sweat, described in JP 2010-046196A, uses an elongate body of absorbent material to draw up sweat produced by a wicking action. In order to measure the sweat production, the absorbent material is impregnated with a colour indicator which changes colour when a certain amount of sweat is collected. This device is therefore reliant on chemical changes as well the use of materials having the correct properties to allow incorporation of chemical indicators thereon while retaining its wicking abilities in order to be effective. It also implies a single use.